Magnetic oxide particles with gold nanoshells: Synthesis, properties and cytotoxic effects

Abstract In this paper, a successful synthesis and detailed study of complex Mn-Zn ferrite core-shell nanoparticles, whose shell is composed of primary silica layer and secondary gold coating, are presented. Magnetic cores with chemical composition Mn 0.61 Zn 0.42 Fe 1.98 O 4 and high specific magnetization are synthesized as a single-phase product by hydrothermal procedure. The cores are embedded in amorphous silica by a modified Stober process, and gold shell is formed on their surface by a seed-and-growth synthesis. Analysis of intermediates and the final product by transmission electron microscopy reveals the course of the multistep synthesis. Energy dispersive X-ray spectroscopy, ICP-MS, and magnetic measurements provide coherent results on the chemical composition of the prepared particles. Colloidal stability of the complex particles in water is evidenced by dynamic light scattering and explained on the basis of zeta-potential measurements. In order to demonstrate the possibility of further functionalization, 4-mercaptobenzoic acid and 7-mercapto-4-methylcoumarin are covalently attached to the surface of the particles. Both the molecules provide strong SERS signals, and the nanoparticles modified with the coumarin derivate constitute an efficient label for fluorescence microscopy. Finally, biological study on two different cell lines is carried out, dealing with the viability and real-time monitoring of proliferation and adhesion of cells. The results indicate only weak cytotoxic effects, and cell viabilities remain generally higher than 90%. Moreover, fluorescence microscopy demonstrates an extensive internalization of the nanoparticles.